1. Field of the Invention
The invention relates to an image forming apparatus such as a copier, a laser beam printer or a facsimile apparatus, and particularly to an image forming apparatus in which the opening and closing of an openable and closable member are detected.
2. Description of Related Art
An openable and closable cover and an opening and closing detecting mechanism according to the conventional art will hereinafter be described in detail with reference to FIG. 7 of the accompanying drawings. FIG. 7 is a schematic view of the openable and closable cover mechanism of a laser beam printer according to the conventional art.
In FIG. 7, the reference numeral 101 designates the main body of the apparatus, and the reference numeral 102 denotes an openable and closable cover. The openable and closable cover 102 is assembled to the main body 101 of the apparatus for rocking movement with a rocking movement support shaft 107 as a fulcrum. A restraining member 108 for restraining the openable and closable cover 102 on the main body 101 of the apparatus is assembled to the openable and closable cover 102 for rocking movement with a rocking movement support shaft 109 as a fulcrum. The reference numeral 106 designates a switch for detecting the opening and closing of the openable and closable cover 102, and the reference numeral 105 denotes a holder for holding the switch 106. The holder 105 is fixed to the main body 101 of the apparatus by a positioning boss 101c provided in the main body 101 of the apparatus. The openable and closable cover 102 is turned from its opened state to its closed state about the rocking movement support shaft 107, whereby the restraining member 108 is rocked with the rocking movement support shaft 109 as a fulcrum and a hook portion 108a is hooked on a lock portion 101b, whereby the openable and closable cover 102 is restrained in its closed state on the main body 101 of the apparatus. A pressure member 104 assembled to the openable and closable cover 102 pressed the switch 106, which thus detects the closed state of the openable and closable cover 102.
Also, when the grip portion 108b of the restraining member 108 is raised, the restraining member 108 rocks about the rocking movement support shaft 109 and the hook portion 108a is disengaged from the lock portion 101b to thereby release the restraint of the openable and closable cover 102. When the released openable and closable cover 102 is turned to its opened state, the pressure member 104 releases its pressure against the switch 106 to thereby detect the opened state of the openable and closable cover 102.
However, the above-described conventional art has suffered from a problem as will be described below.
In recent years, the structure of the laser beam printer has become complicated, and numerous parts are interposed between the switch 106 and the pressure member 104 as will be seen from the assembling tolerance of the holder 105 to the main body 101 of the apparatus, the assembling tolerance of the openable and closable cover 102 to the main body 101 of the apparatus, the assembling tolerance of a positioning member (such as the positioning boss 101c) and the pressure member 104 to the openable and closable cover 102, and so on, and the tolerances of the respective parts affect the accuracy of the positional relationship between the switch 106 and the pressure member 104.
That is, in the main body 101 of the image forming apparatus, it is difficult to improve the accuracy of the positional relationship between the switch 106 for detecting the opened and closed states of the openable and closable cover 102 and the pressure member 104 for pressing the switch 106 provided in the main body 101 of the apparatus.
Therefore, there is the possibility of causing a malfunction due to an erroneous detection that in spite of the openable and closable cover 102 having been closed, the switch is not pressed but the opened state is detected and the printer does not operate or although the openable and closable cover 102 is not properly closed, the closed state thereof is detected and the printer operates. Particularly, in the case where the openable and closable cover 102 serves also as a part of a conveying route for a sheet, although an openable and closable guide is not in its regular closed state, its closed state is detected to thereby cause a jamming of the sheet.
It is a first object of the present invention to provide an image forming apparatus in which the opened and closed states of an openable and closable member are reliably detected.
It is a second object of the present invention to provide an image forming apparatus having an openable and closable member openable and closable relative to the main body of the apparatus, and detecting means for detecting the opened and closed states of the openable and closable member, the openable and closable member having an engagement portion engaged with the detecting means, one of the detecting means and the engagement portion of the openable and closable member being movable relative to the other.
It is a third object of the present invention to provide an image forming apparatus having a first openable and closable member openable and closable relative to the main body of the apparatus, a second openable and closable member openable and closable relative to the main body of the apparatus, and detecting means for detecting the opened and closed states of the first openable and closable member and the second openable and closable member, wherein the detecting means detects the closed state only when both of the first openable and closable member and the second openable and closable member have been closed.
Further objects of the present invention will become apparent from the following description